The present inventor has spearheaded the adoption of electrical transient surge protectors in plug-in adapters inserted between the usual watt-hour meter and its socket, as disclosed in his copending patent applications, Ser. No. 923,524 filed 28 Oct. 1986 for Electrical Transient Surge Protection, and Ser. No. 185,584 filed 22 Apr. 1988 for Electrical Transient Surge Protection in Meter Adapters. Surge protection may be installed instead (or in addition) at nearby upstream locations, such as a weatherhead, or downstream locations, such as a power panel, and may either be built-in or added thereto in prepackaged form. Applicant's disclosed embodiments of meter adapters utilize varistors or equivalent non-linear resistance means as components in their usual disklike form or partially prepackaged.
A common feature of packaged forms of surge protectors is lack or inadequacy of internal fusing. A metal oxide varistor can pass considerable surge current to ground and thereby protect downstream equipment, but repeated conduction of such surge currents increases the likelihood of failure in associated equipment or in the surge protection means itself if cooling time and paths are not present. Varistors may get so hot therefrom as to reach a characteristic failure temperature, resulting in loss of physical integrity--and perhaps explosively. Rather than rely upon installers to provide adequate fusing, it is preferable to include in the package one or more fuses especially selected to function optimally in such use.
The present inventor has pioneered in fusing varistors used for electrical transient surge protection, including distributed resistance fuse links in his first two noted patent applications. He also began the use of temperature-responsive or "thermal" fuses or similar cutoff devices in surge protection, as in the fourth of his aforementioned patent applications, for Safeguarding Electrical Transient Surge Protection.
The present inventor also has increased the current-carrying capacity of surge protectors in small housings by stacking varistor disks in parallel circuit therein, as in the third of his noted patent applications, entitled Electrical Transient Surge Protection.